Grinspoon famously outed Carl Sagan after his death. Sagan appeared in Marihuana Reconsidered as "Mr. X." In 1973, Grinspoon testified in behalf of John Lennon at the Beatle's immigration hearing. The U.S. was attempting to deport Lennon, who'd been arrested for hash in England.

Dr. Grinspoon's a longtime member of the NORML board of directors and, even at his advanced age, regularly attends conferences - in person or via Skype. He lives with is wife Betsy in Wellesley, Massachusetts.